The present invention relates to a machine for processing tobacco bales or slices.
Currently, in lines for processing tobacco at the manufacturing level, raw tobacco bales are broken up by means of a process that is commonly known as slicing and direct conditioning process.
The tobacco bales, once freed from their packaging, depending on their dimensions may be subjected to slicing, so as to reduce them to dimensions that are compatible with the machines designed to process them.
The tobacco slices or intact bales are then conveyed to a known type of machine, designated by the reference numeral 1 in FIGS. 1 and 2, which is conveniently constituted by a frame 2 that is shaped like a cylinder or a rotating drum.
This known type of machine 1 for processing tobacco bales or slices must break them up, heat the resulting intermediate product, designated by the reference numeral 3, to the intended temperature, maintain its temperature for a preset time, known as transit time, and finally humidify the intermediate product until a preset level of humidity is reached.
The cylindrical frame 2 rotates about its own axis, which is conveniently inclined downward so as to allow the simultaneous advancement of the tobacco inside the cylinder.
The tobacco is moved by means of a plurality of radial rods, designated by the reference numeral 4, which protrude inside the cylinder and are suitable to lift the intermediate product 3.
The product, once it has reached a position that is proximate to the upper end of the cylinder, falls back, forming a downward stream 5, which by way of the inclination of the axis falls in a more advanced position along the axis of the cylinder.
In these conventional machines 1 there are provided, at one or both ends of the cylindrical frame 2, one or more nozzles, designated by the reference numeral 6, which are adapted to introduce steam or atomize water by means of steam or compressed air (using therefore two paired nozzles) so as to both humidify and heat the intermediate product 3.
The nozzles 6 are advantageously constituted by double water/steam or water/compressed air nozzles, in which the gaseous element is designed to atomize the water.
Moreover, the machine 1 is advantageously provided with an external duct 7, which comprises a fan 8 and is adapted to generate a current of air that flows, inside the cylinder, in equicurrent or countercurrent with respect to the flow of tobacco, so as to render the humidification and/or heating of the intermediate product 3 as uniform as possible.
In these conventional machines 1, the transit speed and therefore the retention time of the tobacco are determined first of all by the degree of inclination of the drum-like or cylindrical frame 3 and by the speed at which the air and the steam or water are introduced at the ends of the cylinder.
Depending on all of the above variables, a curve is generated which characterizes the behavior of the temperature in the environment inside the cylinder.
For optimum treatment of the tobacco, this temperature should have a behavior that has a peak at the input end, a subsequent constant behavior up to 80–85% of the length of the cylinder, and finally a decrease in the temperature in the output region, where an injection of conditioning water is usually provided.
The main drawback of these conventional tobacco processing machines 1 is that the direct conditioning systems with which they are equipped, described briefly above, often perform a scarcely effective humidification and/or heating of the intermediate product 3.
In particular, it is very difficult to control the behavior of the temperature curve along the axis of the cylinder: the injection of the steam, which it the primary cause of the heating of the tobacco, causes only at the ends of the drum-like frame a heating that is characterized by two temperature peaks located at the input and output of the cylinder and by a central trough that covers most of the length of said cylinder.
The current of optionally preheated air, which should convey steam and water along the entire extension of the cylinder, is in practice scarcely effective in equalizing the temperature behavior.
Moreover, it worsens the drawback constituted by the difficulties in controlling the transit time of the tobacco inside the machine, since it acts differently depending on the characteristics of the tobacco being treated.
In particular, the transit time can be altered by the air stream due to the different density of the tobacco, since there is a greater or smaller propulsion effect (in the case of an equicurrent air stream) or a greater or smaller slowing or retention effect (in the case of a countercurrent air stream) depending on the greater or lower lightness of the tobacco.
Another drawback consists in that the weight and consistency of the tobacco in transit cause a variation in the transit speed also as a function of the number and arrangement of the nozzles 6 for the injection of the steam and water from the ends of the frame.
More specifically, injection at the loading end tends to increase the advancement speed of the intermediate product, while injection at the unloading end tends to retain the tobacco inside the cylinder.
Some conventional machines 1 can be equipped with mechanical means adapted to adjust the transit speed according to the quality and characteristics of the tobacco; however, such mechanical means are highly ineffective, since they assume a control of the rotation rate or inclination of the cylinder.
Actually, the inclination of the axis is usually fixed, and even if it were made variable it could not be adjusted continuously and at the same time effectively in order to cope with the sometimes rapid behavior variations that depend on the quality of the product being treated.
Moreover, the range available for varying the speed of the cylinder is very limited, since in order to properly form the falling stream 5 the product must fall from a rather narrow region of the upper end of the cylinder, designated by the angle α in FIG. 2.
As a partial remedy to the above-described drawbacks, machines for treating tobacco are known which are designated by the reference numeral 11 in FIGS. 3 and 4 and have a device 12 for injecting steam and water that is advantageously constituted by one or more tubes 13 arranged inside the cylindrical frame, designated by the reference numeral 14.
The tubes 13 are supported at their free ends and have, along part or all of their length, suitable nozzles 15 for injecting steam, so as to achieve an injection direction that is approximately perpendicular to the advancement direction of the intermediate product, designated by the reference numeral 16 in the figures.
In this manner, the influence of the steam injection on the transit speed is reduced and at the same time the use of an air current for entrainment along the axis of the cylinder is rendered substantially unnecessary.
The tubes 13 are usually arranged in the opposite position with respect to the product fall region, designated by the reference numeral 17 in FIGS. 3 and 4.
One drawback of conventional machine 11 is the fact that it is often difficult to insert one or more tubes 13, which are necessary of the self-supporting type, along the entire length of the frame 14, which can in some cases exceed ten meters.
Another important drawback is that the radial rods, generally designated by the reference numeral 18, which protrude inside the cylinder and are designed to move and lift the intermediate product 16, force to place the tubes 13 so that they are far from the internal surface of the cylinder, in order to avoid interference with the rods 18.
Due to the length of the rods 18, therefore, the tube 13 cannot be placed in the position that is most convenient to allow optimum steam injection.
Another severe problem can be due to the continuous impact between the tobacco slices or bales and the tubes 13, which can lead to an excessive mechanical stress of said tubes and therefore to consequent malfunctions or breakdowns of said machine 11.
A further drawback of the conventional machines 11 is that leaves or strips of tobacco, designated by the reference numeral 19 in FIG. 4, can straddle said one or more tubes 13 and remain there until they are removed by chance by additional incoming intermediate product 16 or until the machine is cleaned at the end of the production cycle.
In the first case, the tobacco retained by the tube 13 is humidified excessively, and its return to the main stream of intermediate product 16 generates a critical quality problem.
In the second case, instead, a possibly considerable quantity of intermediate product is wasted.
There are known mechanical means for limiting the straddling of the leaves or for cleaning the tube 13 continuously, such as for example periodic or continuous rotation of the tube, the arrangement of rotating cleaning brushes, usually located above the tube, or the arrangement of curved tile-shaped protections above the tube.
However, all these mechanical means are very complicated and scarcely effective and require considerable maintenance.